credentials/alts: Refer to ALTS gRPC types by a different package (#2028)
credentials/alts: Refer to ALTS gRPC types by a different package (#2028)


grpc/grpc-go,thinkerou/grpc-go,grpc/grpc-go,dfawley/grpc-go,stanley-cheung/grpc-go,stanley-cheung/grpc-go,MakMukhi/grpc-go,thinkerou/grpc-go,menghanl/grpc-go,improbable-io/grpc-go,MakMukhi/grpc-go,menghanl/grpc-go,improbable-io/grpc-go,dfawley/grpc-go